Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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074 FXUS61 KPBZ 082314 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 714 PM EDT Tue Jul 8 2025 .SYNOPSIS... A meandering boundary remains in our region into the weekend, with occasional shower and thunderstorms chances. Locally heavy rainfall remains possible at times, with severe thunderstorm chances remaining fairly limited. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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KEY MESSAGES: - Dry weather favored overnight - Fog development expected again tonight --------------------------------------------------------------- As the surface boundary settles near to just south of Interstate 68 and the upper shortwaves remains east, the region is favored to experience dry weather overnight as subsidence aloft takes hold. The approach of a western Great Lakes trough will attempt to increase high to mid level clouds starting around midnight through Wednesday morning; timing and thickness of these clouds layers will play a critical role in the development and areal coverage of fog. Latest model guidance favors river valley locations and locations south of Pittsburgh where limited dry intrusion occurred behind the front. Given uncertainty in the spacial coverage and impacts of incoming higher cloud decks will preclude any fog hazard products at this time.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... KEY MESSAGES: - Stalled boundary keeps most of the isolated convection south of Pittsburgh on Wednesday. - Better coverage of scattered storms Thursday as boundary lifts back north. - Temperatures just above normal. ---------------------------------------------------------------- The boundary likely continues to meander south of our region Wednesday, keeping the deeper moisture/instability to the south and east. Some isolated diurnal convection remains possible, although model soundings show some limited capping potential in the middle levels, keeping a lid on coverage. Any limited severe potential would exist in portions of northern West Virginia, where better instability/stronger updraft potential would lie, along with any potential for localized heavy rainfall, but the overall threat appears quite low. Temperatures should rise a degree or two as compared to today, given incipient weak southwest flow. Convection fades Wednesday night, with Thursday likely dawning dry. A crossing shortwave trough should begin to push the boundary north again as a warm front, with a bit more widespread diurnal convective coverage possible. Skinny CAPE profiles and low shear suggest that the severe threat remains low, but that localized high rainfall rates remain possible, especially as PWAT levels begin to recover. && .LONG TERM /FRIDAY THROUGH TUESDAY/... KEY MESSAGES: - Stalled boundary lingers into the weekend at least with continued daily rain chances, currently highest Sunday. - Low rain chances next week as pattern uncertainty increases. - Continued near to above-normal temperature. ------------------------------------------------------------------- On Friday, a wave of low pressure along the boundary may push it back south of Pittsburgh, perhaps towards the Mason-Dixon Line. This would keep higher diurnal shower/storm chances across our southern zones. Precipitable water remains elevated near and south of the boundary, with a reasonable range of 1.3 to 1.6 inches, so locally heavy rainfall will remain possible. More organized surface low pressure likely lifts across the western Great Lakes on Saturday, which would push the boundary back north, before a potential cold frontal passage Saturday night or Sunday. There remains ensemble disagreement on how this could play out, particularly with the timing. For now, Sunday appears to have better rain chances than Saturday, and given the FROPA uncertainty, the second half of the weekend also has greater high temperature uncertainty. NBM 10th to 90th percentile spreads exceed 10 degrees for most of the region, with possible max values ranging from around 80 to the lower 90s. Severe potential will depend on timing as well, with ensemble soundings and machine learning advertising at least low-end potential - forecast deep shear remains on the low side, limiting organized convection potential. Localized heavy rain remains possible as well. Uncertainty them propagates into next week. Elevated 500mb heights and zonal flow aloft are most likely, keeping temperatures near to above normal, but differences in disturbances in that flow require low-end PoPs for both Monday and Tuesday. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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The surface front has dipped south of all area terminals, which will allow upper subsidence to erode residual stratocu through midnight and maintain VFR conditions. Uncertainty significantly raises for the 06z-12z period regarding the areal coverage and degree of intensity for fog formation. Factors favoring fog include enough boundary layer moisture, very light wind, and a period of clearer skies fostering strong radiational cooling. Factors that could limit fog include the influx of mid-high level clouds overnight ahead of the next shortwave and its timing to disrupt cooling processes. TAFs are trended toward a less foggy solution, but probabilities remain high enough for IFR/LIFR vis mention at river valley sites or terminals that saw minimal dry advection. Diurnal heating/mixing will erode any fog/low stratus by 15z, with VFR expected the rest of the day. Shortwave movement is likely to be displaced too far north/south to generate but a low probability (20%) shower between 18z-00z that isn`t worth TAF mention at this time. Outlook... A weakly forced but warm/humid environment is favored through the end of the week that will allow for periods of showers/thunderstorms along with dry periods; confidence is likely to be lower on timing various rounds of precipitation as well as the resultant cig/vis impact they could have during the morning hours. More significant upper level and surface boundary movement appears to arrive over the weekend that will create a more focused and better timed period for convection and restriction development.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...MLB/CL NEAR TERM...Frazier SHORT TERM...CL LONG TERM...CL AVIATION...Frazier